In order to explore the potential utilization value of iron tailings, the typical solid waste-iron tailings was introduced into rigid polyurethane foam (RPUF) as a flame retardant filler in this paper. The flame retardant performance, combustion performance, gas-phase products and char residue’s related properties of RPUF/ITS composites were systematically investigated by limiting oxygen index, thermogravimetric (TG), cone calorimetry (CCT) and thermogravimetric-infrared spectrometry (TG-FTIR). The results showed that ITS improved the overall thermal stability of the composites, and the T-5%, T-50%, Tmax1, Tmax2 and char residue rates were all higher than those of the pure samples. The CCT indicated that ITS had a certain effect on smoke suppression and heat release reduction. The peak heat release rate of RPUF-6 was reduced by 22.75% compared with that of the pure sample, and the total smoke release of RPUF-2 was reduced by 25.36%. Smoke factor (SF), fire growth rate index and fire performance index indicated that ITS reduced the fire risk of RPUF/ITS composites. TG-FTIR showed that ITS inhibited the decomposition of RPUF/ITS composites, and the release intensity of hydrocarbons, CO2, isocyanate compound, CO, aromatic compounds and esters decreased significantly. TG, MCC, scanning electron microscope and Raman implied that ITS promoted the formation of a dense char layer in RPUF and improved the heat resistance of the char layer.

Rigid polyurethane foam (RPUF) has many excellent properties, but its flammability has been a challenge for the application of RPUF compounds. In this research, piperazine pyrophosphate (PAPP) and expandable graphite (EG) were added to the RPUF matrix to improve the fire performance of RPUF. Thermogravimetric analysis (TGA) revealed that PAPP and EG contributed to the early decomposition of the FR‐RPUF matrix, and the char residue of RPUF‐3 reached 37.1 wt% when the PAPP: EG ratio was 1:1. The flame‐retardant test indicated that the FR‐RPUF composites reached the V‐0 level, and the limiting oxygen index (LOI) value of RPUF‐4 was 28.8%. In addition, cone calorimeter tests showed that the addition of flame retardants reduced the peak heat release rate (PHRR) and total heat release (THR), further improving the fire performance of the compounds. The analysis of the char residue confirmed the formation of a denser char residue and significant improvement in the graphitization degree due to the PAPP/EG synergistic effect, indicating that the char residue could effectively isolate oxygen and heat and act as a flame retardant in the condensed phase.